Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine that is released by T-cells and macrophages. It is viewed to play a key role in a wide range of diseases including rheumatoid arthritis, sepsis, atherosclerosis, asthma, and acute respiratory distress syndrome. MIF also is involved in cell proliferation and differentiation, and anti-MIF antibodies suppress tumor growth and angiogenesis. The biology of MIF and potential biomedical significance of MIF-inhibition are striking, as reviewed elsewhere. Orita, et al., (2002), Macrophage migration inhibitory factor and the discovery of tautomerase inhibitors, Curr. Pharm. Res. 8, 1297-1317 (“Orita 2002”); Lolis, et al. (2003), Macrophage migration inhibitory factor, Expert Opin. Therap. Targets 7, 153-164; Morand, et al., (2006), MIF: a new cytokine link between rheumatoid arthritis and atherosclerosis. Nature Rev. Drug Disc. 5, 399-411. The crystal structure for MIF, which was solved by Prof. Elias Lolis at Yale, revealed a new structural superfamily (Sun, H. et al. (1996) Crystal structure at 2.6-A resolution of human macrophage migration inhibitory factor. Proc. Nat. Acad. Sci. USA 93, 5191-5196; Lolis, E. & Bucala, R. (1996) Crystal structure of macrophage migration inhibitory factor (MIF), a glucocorticoid-induced regulator of cytokine production, reveals a unique architecture. Proc. Assoc. Amer. Physicians 108, 415-9); the 114-residue MIF monomer has a β/α/β motif and three monomers associate to form a symmetrical trimer. The trimer is toroidal with a solvent-filled central channel. MIF was also found to show structural homology to two prokaryotic tautomerases, and phenylpyruvate and D-dopachrome were discovered to be MIF tautomerase substrates. Rosengren, E.; et al., (1996) The immunoregulatory mediator macrophage migration inhibitory factor (MIF) catalyzes a tautomerization reaction. Molec. Med. 2, 143-149; Rosengren, E.; et al. (1997), The macrophage migration inhibitory factor MIF is a phenylpyruvate tautomerase. FEBS Lett. 417, 85-8.

Though L-dopachromes are substrates for a response mechanism of invertebrates to microbial invasion, the catalytic activity of mammalian MIF is likely vestigial. Site-directed mutagenesis and crystallography have identified the MIF active site, and mechanisms for the tautomerase activity have been proposed with key roles for Prol as a base and Lys32 as a proton donor (Lubetsky, J. et al. (1999), Pro-1 of macrophage migration inhibitory factor functions as a catalytic base in the phenylpyruvate tautomerase activity. Biochemistry 38, 7346-54; Lolis, et al. (2003), Macrophage migration inhibitory factor, Expert Opin. Therap. Targets 7, 153-164). Each MIF trimer has three tautomerase active sites, which are well defined cavities located at the interfaces of the monomer subunits. There is also evidence that the interaction of MIF with its receptor, CD74, occurs in this vicinity and MIF inhibition is often directly competitive with MIF-CD74 binding. Senter, P. D., et al., (2002) Inhibition of macrophage migration inhibitory factor (MIF) tautomerase and biological activities by acetaminophen metabolites. Proc. Nat. Acad. Sci. USA 99, 144-9 (“Senter 2002”). However, some potent tautomerase inhibitors do not inhibit the biological activity of MIF (Senter 2002).
Discovery of small molecule inhibitors of MIF is clearly important to provide further probes into the biology of MIF and potential therapeutic agents for MIF-related diseases. As reviewed in Orita 2002, initial efforts provided some dopachrome (Zhang, X. & Bucala, R. (1999), Inhibition of macrophage migration inhibitory factor (MIF) tautomerase activity by dopachrome analogs. Bioorg. Med. Chem. Lett. 9, 3193-3198), glutathione, and hydroxycinnamate analogs in the μM to mM range. Subsequently, a virtual screening exercise with the DOCK program on the Available Chemicals Directory, followed by purchase and assaying of 524 compounds delivered 14 leads with Ki values below 10 μM. However, the diversity is low since all 14 compounds are coumarin derivatives or close analogs (Orita, M., et al. (2001). Coumarin and Chromen-4-one Analogues as Tautomerase Inhibitors of Macrophage Migration Inhibitory Factor: Discovery and X-ray Crystallography. J. Med. Chem. 44, 540-547). Coumarins are generally viewed as poor drug leads owing to their promiscuity as protein binders. These authors also reported a crystal structure for a 7-hydroxycoumarin derivative complexed with MIF. Shortly thereafter, the activities of several phenyl-dihydroisoxazoles were published along with the crystal structure for the MIF complex with the most potent one, ISO-1 (Lubetsky, J. B. et al. (2002), The tautomerase active site of macrophage migration inhibitory factor is a potential target for discovery of novel anti-inflammatory agents. J. Biol. Chem. 277, 24976-24982). A key feature in the X-ray structures is a hydrogen bond between the phenolic OH and the side-chain CO of Asn97, which forms a backstop for the active site channel. Further optimization enhanced the potency from 7 μM for (R)-ISO-1 to 550 nM for (R)-17 (Cheng, K. F. & Al-Abed, Y. (2006) Critical modifications of the ISO-1 scaffold improve its potent inhibition of macrophage migration inhibitory factor (MIF) tautomerase activity. Bioorg. Med. Chem. Lett. 16, 3376-3379).

PCT WO2006045505 discloses MIF inhibitors. The MIF inhibitors of PCT WO2006045505 are 3,4-dihydro-benzo[e][1,3]oxazin-2-ones which are substituted at the nitrogen atom by unsubstituted or substituted (C3-8)cycloalkyl, (C1-4)alkyl(C3-8)cycloalkyl, (C6-18)aryl or (C6-18)aryl(C1-4)alkyl. PCT WO2007070961 discloses MIF-inhibiting benzimidazolone analogues and derivatives.
Given the extent and severity of MIF-associated disorders, there is a continuing need for novel compounds, pharmaceutical compositions, and methods of treatment that modulate levels of MIF expression.